The desire to integrate data, voice, image and video over high speed digital trunks had led to the development of a packet switching technique called cell relay or asynchronous transfer mode. A typical fully integrated voice and data network using digital trunk lines includes a number of geographically distant interconnected switches. Each switch acts as a cell exchanger for receiving and forwarding cell information to its destination. By the use of a variety of interface cards, each switch is capable of interfacing to user generated voice and data streams, then segmenting and assembling the streams into a more efficient cell format for transmission over a closed network using digital lines. Each switch is also capable of receiving data from other network nodes and forwarding that data through to other network switches to its ultimate destination. All terminal switches also provide the necessary interface cards required to reassemble the data contained in the cells into standard user data stream formats.
In general, each ATM switch in the network comprises a switching fabric and a plurality of ports. The ports are coupled to various input and output lines and act as interfaces for relaying the ATM cells. The switching fabric couples the various ports to one another, thereby allowing for the routing of ATM cells within the switch. The switching fabric typically includes a number of processors and other controllers, all of which need to communicate with one another. To accommodate this arrangement, ATM switches generally employ two system wide buses: a cell bus, and a control bus.
The cell bus is generally a high speed bus used for switching cells between ports. The control bus transports data and control information between the various processors and port controllers within the switch. This arrangement of two distinct buses, one for cell switching and one for passing control and data between the switch processors, leads to increased costs and complexity for ATM switches. Therefore, it would be desirable to integrate the transfer of ATM cells and inter-processor communications within a single system bus in an ATM switch.